Southern California is home to a half-dozen congressional districts where the fate of Republican seats could help decide which of the two major parties wins control of the U.S. House.

Nearly all of the districts are in Orange County, the once staunchly conservative region undergoing demographic changes that are nudging the county more to the left. In 2016, for the first time in 80 years, Orange County favored a Democrat for president.

Two incumbent GOP congressmen — Darrell Issa and Ed Royce — announced earlier this year that they were stepping down from office. Their decision opened up the field to a rush of congressional hopefuls from both parties.

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